Interfacing RF Module with 8051 Microcontroller- (Part 15/45)

Requirements:

2. RF module (433 MHz Rx/Tx)

3. Encoder/Decoder IC (HT12E/D)

6. 11.0592 MHz crystal

7. 4X4 keypad

This project is about interfacing RF (Radio Frequency) module with the 8051 microcontroller. These RF modules help us in sending and receiving the data wirelessly up to certain distance thereby offering ease in wireless data transferring. There are many forms of wireless technologies which can transfer the data such as Bluetooth modules, ZigBee modules, and Wi-Fi modules.

RF is one of these technologies that can be availed at a much less cost and works quite well for small scale projects. These modules are really easy to deal with as they just require the data to be transferred serially and VCC+GND supply of course.

Prototype of 8051 Microcontroller based RF Data Transmission

Fig. 1: Prototype of 8051 Microcontroller based RF Data Transmission

In this project, I have also made use of the encoder/decoder IC (HT12E/D) to transfer the parallel 4 bit data serially.

A 4X4 keypad sends the signals to the microcontroller on pressing any digit. The microcontroller then analyses the digit pressed and sends the corresponding 4 bit data to the encoder which further sends the serially packed data to the RF transmitter part. This was the transmitter part of my project.

Image of RF data transmitter based on HT12E encoder IC

Fig. 2: Image of RF data transmitter based on HT12E encoder IC

Talking about the receiver’s end; the RF Receiver part receives the signals from the previous transmitter in serial format. These signals are then fed to the decoder IC which parallelizes the data into 4 bits so that they can be read by the microcontroller to perform further operations. When a 4 bit data is received by the microcontroller it analyses the data and displays the corresponding character value on 16X2 LCD.

Image of RF data receiver based on HT12D decoder IC

Fig. 3: Image of RF data receiver based on HT12D decoder IC

I have connected my Encoder/Decoder ICs to the lower half of PORT 3 of the microcontrollers.

At receiver side the LCD is connected to PORT 2 while the RS, RW and E are connected to pin P1^5, 6 and 7 respectively.

In my coding part I have used three user defined header files: <delay.h>,

<lcd.h> and <keypad.h>

<delay.h>: provides the delay_msec().

<lcd.h>: provides all the functions related to LCD programming.

<keypad.h>: provides the Read_Keypad() which returns the pressed digit on keypad.

Note:

These encoders/decoders can deal with only 4 bit data, thus for sending a higher bit data the ICs should be replaced with the desired one.

Also the TX/RX pin, P3^0, on the microcontrollers can alone transmit/receive data serially, thus removing the encoder/decoder ICs from the circuit. But it didn’t work with me, so if anyone knows how to do it please let me know.

Applications:

This technology can be used to make wireless control systems like door locks, operating home appliances wirelessly and much more.

For children, a wireless spy car is the best option!!!

Project Source Code

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TX

#include
#include
void main()
{
char p=0;
while(1)
{
               p=Read_Keypad();
                while(p)
                {             
                                if(p=='1')
                                P3=0x10;
                                if(p=='2')
                                P3=0x20;
                                if(p=='3')
                                P3=0x30;
                                if(p=='4')             
                                P3=0x40;
                                if(p=='5')
                                P3=0x50;
                                if(p=='6')
                                P3=0x60;
                                if(p=='7')
                                P3=0x70;
                                if(p=='8')             
                                P3=0x80;
                                if(p=='9')
                                P3=0x90;
                                if(p=='0')
                                P3=0x00;
                                if(p=='*')
                                P3=0xa0;
                                if(p=='#')            
                                P3=0xb0;
                                if(p=='A')            
                                P3=0xc0;
                                if(p=='B')            
                                P3=0xd0;
                                if(p=='C')            
                                P3=0xe0;
                                if(p=='D')            
                                P3=0xf0;
                                p=Read_Keypad();
                }
}
}

RX

#include
#include
#include
void main()
{
char p=0;
P3=0xf0;
Lcd8_Init();
while(1)
{                             
                 while(p!=P3)
                                {
                                                p=P3;
                                                Lcd8_Cmd(0x80);
                                                if(p==0x10)
                                                Lcd8_Write_Char('1');
                                                if(p==0x20)
                                                Lcd8_Write_Char('2');
                                                if(p==0x30)
                                                Lcd8_Write_Char('3');
                                                if(p==0x40)
                                                Lcd8_Write_Char('4');
                                                if(p==0x50)
                                                Lcd8_Write_Char('5');
                                                if(p==0x60)
                                                Lcd8_Write_Char('6');
                                                if(p==0x70)
                                                Lcd8_Write_Char('7');
                                                if(p==0x80)
                                                Lcd8_Write_Char('8');
                                                if(p==0x90)
                                                Lcd8_Write_Char('9');
                                                if(p==0x00)
                                                Lcd8_Write_Char('0');
                                                if(p==0xa0)
                                                Lcd8_Write_Char('*');
                                                if(p==0xb0)
                                                Lcd8_Write_Char('#');
                                                if(p==0xc0)
                                                Lcd8_Write_Char('A');
                                                if(p==0xd0)
                                                Lcd8_Write_Char('B');
                                                if(p==0xe0)
                                                Lcd8_Write_Char('C');
                                                if(p==0xf0)
                                                Lcd8_Write_Char('D');
                                }
                }
}

Delay.h

void delay_msec(int time)
{
int i=0;
while(i
//LCD Module Connections
                sbit RS=P1^5;
                sbit RW=P1^6;
                sbit E=P1^7;
//End LCD Module Connections
char *string;
//LCD 8 Bit Interfacing Functions
void Lcd8_Cmd(unsigned char value)
                {
                P2=value;
                RS=0;
                RW=0;
                E=1;
                delay_msec(1);
                E=0;
                }
void Lcd8_Init()
{
  Lcd8_Cmd(0x38);    //function set
  Lcd8_Cmd(0x0C);    //display on,cursor off,blink off
  Lcd8_Cmd(0x01);    //clear display
  Lcd8_Cmd(0x06);    //entry mode, set increment
}
void Lcd8_Write_Char(unsigned char value)
                {
                P2=value;
                RS=1;
                RW=0;
                E=1;
                delay_msec(1);
                E=0;
               }
void Lcd8_Write_String(char *a)
{
                int i;
                string=a;
                for(i=0;a[i]!='';i++)
                Lcd8_Write_Char(a[i]);
}

Keypad.h


sbit R1 = P1^7;
sbit R2 = P1^6;
sbit R3 = P1^5;
sbit R4 = P1^4;
sbit C1 = P1^3;
sbit C2 = P1^2;
sbit C3 = P1^1;
sbit C4 = P1^0;
//End Keypad Connections
char Read_Keypad()
{
  C1=C2=C3=C4=1;
  R1=0;
  R2=1;
  R3=1;
  R4=1;
  if(C1==0){while(C1==0);return '1';}
  if(C2==0){while(C2==0);return '2';}
  if(C3==0){while(C3==0);return '3';}
  if(C4==0){while(C4==0);return 'A';}
  R1=1;
  R2=0;
  R3=1;
  R4=1;
  if(C1==0){while(C1==0);return '4';}
  if(C2==0){while(C2==0);return '5';}
  if(C3==0){while(C3==0);return '6';}
  if(C4==0){while(C4==0);return 'B';}
  R1=1;
  R2=1;
  R3=0;
  R4=1;
  if(C1==0){while(C1==0);return '7';}
  if(C2==0){while(C2==0);return '8';}
  if(C3==0){while(C3==0);return '9';}
  if(C4==0){while(C4==0);return 'C';}
  R1=1;
  R2=1;
  R3=1;
  R4=0;
  if(C1==0){while(C1==0);return '*';}
  if(C2==0){while(C2==0);return '0';}
  if(C3==0){while(C3==0);return '#';}
  if(C4==0){while(C4==0);return 'D';}
 return 0;
}

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